Shipwreck hunters will make a new expedition to the Abrolhos Islands in a bid to solve the 300-year-old mystery of the lost Dutch ship the Aagtekerke, which is thought to have gone down along the WA coast.
Hugh Edwards and his team believe the Aagtekerke struck Half Moon Reef in the archipelago off Geraldton when it disappeared en route to Indonesia in 1726.
Next month they hope to find some of the three tonnes of silver coins the ship was carrying between the Cape of Good Hope and Jakarta that could prove the wreck is in the Abrolhos Islands.
In light of the growing evidence gathered by Mr Edwards and his team, WA Museum maritime archaeologists are now also planning to survey the archipelago.
In 1968, Mr Edwards was among the finders of the Zeewijk, which sank on Half Moon Reef in 1727.
But the discovery of elephant tusks, which were not listed on the Zeewijk's inventory but were part of the Aagterkerke's cargo, has led experts to believe the reef could be home to both wrecks.
"We have looked all over the archipelago for the other ship but have never been able to find it," Mr Edwards said.
"So we have come to the conclusion there are two wrecks at that site."
Mr Edwards said they also found 44 guns at the Zeewijk wreck site, more than the usual number of 36 on such a ship. Nine anchors were also found when the Zeewijk would not usually have had more than six.
"The Aagtekerke loaded 214 elephant tusks as part of the cargo at the Cape of Good Hope," Mr Edwards said.
"The Zeewijk did not have elephant tusks. But among the difficulties is that both ships were built in the same shipyard by the same shipwrights.
"They are identical ships so we have got to look for different factors."
Mr Edwards said if his team found coins, he believed they would be from the Aagtekerke because all the coins the Zeewijk had been carrying were salvaged, recorded and returned to the owner, the Dutch East India Company.
Mr Edwards and his team have made four expeditions to the wreck site since 2009 in a bid to solve the Aagtekerke mystery.
Diving in the area is not easy with big surf and strong currents common.
WA Museum chief executive Alec Coles said there was enough evidence for the museum's maritime archaeologists to join the search for the Aagtekerke.
"It's a compelling story and one that we need to be able to at least confirm or refute, remembering there has been no significant Dutch shipwreck discovery probably in 40 years in WA," he said.
"This would be really significant if we were able to prove it."
Mr Coles said the museum was working with the Dutch Embassy and Mr Edwards to study original documentation from the ships to get clues about what might identify the Aagtekerke.
The ship's crew of 212 were lost when it disappeared after leaving the Cape of Good Hope on January 27, 1726, but the news did not reach their families in the Netherlands until July the following year.
The Zeewijk was wrecked on Half Moon Reef on June 9, 1727.
The survivors built a second ship, the Sloepie, and 82 of the original crew of 208 reached Jakarta on April 30, 1728.